Apple scab, which is caused by Venturia inaequalis (Cooke) G. Wint., is a destructive disease that affects apples (Malus × domestica Borkh.). To develop an approach to breeding apples for scab resistance, race distribution of V. inaequalis in Morioka, Japan and genetic factors affecting partial scab resistance observed on ‘Akane’ were assessed. An inoculation test using several differential hosts suggested that race 1 of V. inaequalis was the predominant race in Morioka, Japan. To characterize the genetic profile of ‘Akane’ resistance, quantitative trait locus (QTL) analyses that employed two years of natural scab infection scores in a fungicide-free orchard in Kuroishi, Aomori, Japan were performed using an F1 population derived from the ‘Orin’ × ‘Akane’ cross. A QTL allele that explained 20% of the phenotypic variance in scab resistance was detected on chromosome 17 of ‘Akane’. In the middle region of chromosome 17 of ‘Orin’ and in very close proximity to the ‘Akane’ QTL, a weak QTL allele was also detected, which explained 5% of the phenotypic variance observed. We considered that these effects were caused by alleles of the identical QTL. Haplotyping analysis indicated that this QTL resistance allele from ‘Akane’ originated from ‘Worcester Pearmain’.
Tomato yellow leaf curl virus (TYLCV), which causes tomato leaf curl disease, is transmitted by whiteflies. TYLCV tolerant/resistant tomato cultivars have been introduced as effective countermeasures against this serious disease. In the present study, TYLCV infectious clones of the Israel strain and Israel mild strain were used to conduct inoculation tests involving TYLCV tolerant/resistant tomato cultivars/strains, the course of disease symptoms was clarified, and changes in the viral DNA load were quantified using the loop-mediated isothermal amplification method. The inoculation method with infectious clones revealed symptoms and virus growth comparable to those of a conventional inoculation method using whitefly. The results demonstrated that the method could be used for screening tolerant/resistant strains.
This study was conducted to investigate the effects of the length of the light period and photosynthetic photon flux density (PPFD) in the growth chamber on the germination and growth of Eustoma grandiflorum after the wet treatment of seeds at 10°C. Seeds were sown in 200-cell trays, and then the wet treatment was applied for five weeks at 10°C under dark conditions. After this treatment, all seedlings were grown for five weeks in the growth chamber at a temperature of 27.5°C under light/dark conditions. When the average PPFD was 125 μmol・m–2・s–1, the germination rate eight days after transferring the cell tray into the growth chamber was 98% or higher regardless of the length of the light period of 12 to 24 h. After raising the seedlings for five weeks, the seedlings exposed to light periods of 20 and 24 h were significantly larger than at 12 h. For the seedlings grown with light periods of 20 h or 24 h, the number of days until bolting, flower budding, and flowering from transplantation was significantly fewer than at 12 h. When the light period was 24 h, the germination rate eight days after transferring into the growth chamber was about 95% or higher regardless of the PPFD from 50 to 125 μmol・m–2・s–1. The seedlings with PPFD at 100 and 125 μmol・m–2・s–1 were significantly larger than at 50 μmol・m–2・s–1. In seedlings grown with PPFD of 100 and 125 μmol・m–2・s–1, the number of days until bolting, flower budding, and flowering from transplantation was significantly fewer than at 50 μmol・m–2・s–1. Rosette plants were not found under all treatment conditions, and all seedlings bolted and subsequently bloomed. The cut flower characteristic forms were equivalent in both experiments regardless of the treatment. We concluded that the most suitable length of the light period for producing Eustoma grandiflorum seedlings in the growth chamber at a temperature of 27.5°C under light/dark conditions was over 20 h and the most suitable PPFD was 100 to 125 μmol・m–2・s–1.
High temperatures delay flowering in chrysanthemums. This heat delay disturbs stable planning production by light culture in summer. There was a marked difference in the degree of flowering delay caused by high temperature treatment among summer-to-autumn-flowering small-flowered spray-type chrysanthemum cultivars, which are suitable for open-field light culture. In the cultivars showing less delayed flowering caused by high temperature treatments, delay in flowering time also tended to be shorter in the hotter summer during three consecutive years of cultivation by light culture. In open-field light culture of summer-to-autumn-flowering small-flowered spray-type chrysanthemums, stable planning production with little annual fluctuation can be established using cultivars showing less heat delay. In addition, the expression level of the florigen gene (FTL3) promoting flowering was measured under high temperature conditions. In the cultivar showing a marked heat delay, the rise in the FTL3 expression level was strongly suppressed by high temperatures. On the other hand, the FTL3 expression level increased even under high temperatures in the cultivar showing less heat delay. The results suggest that suppression of the florigen gene by high temperatures is involved in the heat delay of flowering in summer-to-autumn-flowering small-flowered spray-type chrysanthemums, as is the case with autumn-flowering chrysanthemums and the wild chrysanthemum Chrysanthemum seticuspe.
In 5 to 6 years after the accident, we investigated the 137Cs activity concentration in the fruit and leaves of Japanese persimmon ‘Hachiya’ at different growth stages. The 137Cs concentration tended to be the highest in young fruit. In mid-September, the 137Cs concentration dropped to the lowest level with fruit growth. After that, the concentration of some fruit gradually increased with their maturation. However, the concentration change after mid-September could not be observed clearly since variation in the individual fruit concentration was large. It was considered that we could reduce the risk of high concentrations by harvesting fruit at a suitable time because we could not deny the possibility of the 137Cs concentration of fruit rising. In the case of leaves, the 137Cs concentration tended to be the highest in young fruit and decrease with growth.
In this study, the effects of sheet-mulching and rootstock on expression of Citrus FLOWERING LOCUS T (CiFT), number of flowers, and yield were investigated in satsuma mandarin ‘Sasebo Unshiu’ grafted on trifoliate orange (Poncirus trifoliata (L.) Raf.) or ‘Hiryu’ (Flying Dragon) for several years. In the analysis of data from a plural year, rootstock and sheet-mulching had no influence on CiFT expression or the number of flowers. On the other hand, in the analysis of data from a respective single year, significant differences were detected in CiFT expression and the number of flowers in some years. Trees both with and without sheet-mulching tended to flower in alternate years, and the pattern in trees with sheet-mulching were opposite to those without sheet-mulching. In the year when trees with sheet-mulching produced more flowers than the average number, those without sheet-mulching had fewer than the average number of flowers, and vice versa. The alternate bearing index in each tree showed that the annual change in the CiFT mRNA level was significantly greater in trees with than without sheet-mulching. These results suggest that sheet-mulching cultivation makes annual floral induction unstable in ‘Sasebo unshiu’ although this instability has no effect on the number of flowers or yield.
The whole harvest cultivation method for one-year-old plants (new cultivation method) is a labor-saving open field asparagus cultivation method that allows growers to produce a high yield of high-quality asparagus at low-cost. Green and purple asparagus production by the new cultivation method is becoming popular in Japan. White asparagus production in Japan is usually based on blanching with soil (SOIL). On the other hand, the film-cover method (FILM) has also become popular in recent years. In this study, for the purpose of introducing the new cultivation method for white asparagus production, green and purple asparagus were examined regarding the effects of blanching and its methods on the yield and quality of spears. The test was conducted both in Nagano and Kanagawa (cold and warm areas, respectively). The yield and rate of thick spears (L or larger size) cultivated by SOIL and FILM in both cold and warm areas were equivalent to or higher than without blanching (WITHOUT BLANCHING). The amount of rutin in spears cultivated by WITHOUT BLANCHING was significantly higher than by SOIL and FILM. The amount of protodioscin in spears cultivated by SOIL was significantly higher than WITHOUT BLANCHING and FILM. From these results, on using green and purple asparagus blanched by SOIL and FILM to cultivate as white asparagus with the new cultivation method, the quality of spears was different from WITHOUT BLANCHING, and the yield and rate of thick spears were equal or higher.
The relationship between red/far-red ratio (R/FR ratio) of LED chips and flowering inhibition, by LED light sources with the same power consumption, was evaluated using two cultivars of chrysanthemum, the autumn flowering ‘Jimba’ and summer-to-autumn flowering ‘Iwano-hakusen’. The combinations of light intensity of the R and FR LED chips emitting at wavelengths of 632 nm and 734 nm, respectively, were set as 5 : 0, 4 : 1, 3 : 2, 2 : 3, 1 : 4, and 0 : 5. The six LED light bulbs were divided into short- and long-term lighting to detect differences in the effects of flowering inhibition due to differences in light quality. The long- and short-term lighting treatments were set at 4 h and 30 min, respectively, for ‘Iwano-hakusen’ and 2 h and 4 min, respectively, for ‘Jimba’. In the short-term lighting treatment, a high flowering inhibitory effect was obtained with the R5:FR0 chip combination in both cultivars. In long-term lighting treatment, the responses to light quality differed between the cultivars: flowering inhibition in ‘Iwano-hakusen’ was highly effective at R3:FR2 and R2:FR3; however, in ‘Jimba’ a marked inhibitory effect was obtained at R5:FR0. Long-term lighting by R + FR light resulted in a high flowering inhibitory effect in ‘Iwano-hakusen’. This suggested the involvement of high irradiation response via the phytochrome phyA.
In this study, we investigated the effects of UV-B intensity and irradiation time on growth, antioxidant activity, and the anthocyanin content of cabbage (Brassica oleracea L.) and perilla (Perilla frutescens (L.)) sprouts. The two plants were grown under four different UV-B intensity levels (0, 100, 200, and 400 mW・m–2). UV-B irradiation was applied in the night-time, daytime or night-time with a fluorescent lamp. In the sprouts of both plants, the hypocotyl length was not affected by UV-B irradiation, but the cotyledon length and fresh weight decreased with an increase in UV-B intensity. However, in perilla, dwarfing of the cotyledon was alleviated when UV-B was irradiated in the daytime or night-time with a fluorescent lamp. For both plants, antioxidant activity tended to increase with an increase in the UV-B intensity level, especially when a fluorescent lamp was used at the same time. Conversely, the anthocyanin concentration increased with an increase in the UV-B intensity level in cabbage; however, in perilla sprouts, UV-B irradiation decomposed anthocyanin. These results suggest that the usefulness of UV-B irradiation in sprout production differs among plant species. Further, it was indicated that UV-B damage to sprouts could be avoided by simultaneous irradiation with visible light.
The conventional timing of night-break-lighting to inhibit flower induction has been at midnight in Chrysanthemum morifolium. In this study, we investigated the light-sensitive time zone of summer-to-autumn-flowering small-flowered spray-type Chrysanthemum, to establish an effective and practical light culture system. The time zones of night-break-lighting were midnight (10:00 pm–2:00 am; the conventional method), an earlier time zone (8:00 pm–12:00 am), and a late time zone (12:00 am–4:00 am). Several cultivars of the August-flowering type by light culture were used for the experiments. Plants were grown in open fields, and an incandescent lamp and a fluorescent lamp were used as light sources. As a result, the most light-sensitive time zone was the late time zone, because it effectively inhibited flower bud initiation. Long-day leaf numbers and number of days to flowering were increased by night-break-lighting in the late time zone. Moreover, the night-break-lighting in the late time zone was the most practical method, since we demonstrated effectively inhibited flower bud initiation in farmers’ fields. For the above reasons, night-break-lighting in the late time zone outperforms the conventional method for the regulation of flowering.
Characteristics of ‘Flowering disorder (erratic flowering)’ in greenhouse-cultivated Japanese pears were investigated from 2014 to 2017 in Fukuoka Prefecture. Trees with 30% or lower flowering rates showed decreases in the fruit number and an infer fruit size, and thus were categorized into the ‘severe’ grade of flowering disorder. We calculated the ‘severe grade tree rate’ as the proportion of trees with a severe grade to the total number of trees in each orchard. When the severe grade tree rate was averaged separately for the orchards without and with heating, the highest rate was 8.6% in 2017 and 16.6% in 2016, respectively. The severe grade tree rate was higher in ‘Kosui’ than ‘Hosui’. In 2016, the severe grade tree rate became lower in greenhouses with the start of vinyl covering of greenhouses. The results suggest that delayed endodormancy breaking is one of the causes of flowering disorder. They also suggest that flowering disorder in greenhouses is influenced by the endodormancy of flower buds.